Table 2. HERV-W env clones obtained from PBMC by standard PCR with primers used in the quantitative PCR.

Status	DNA PCR	DNA PCR	RNA RT–PCR	RNA RT–PCR
	Number of clones with insert	Number of sequences aligned with probe	Number of clones with insert	Number of sequences aligned with probe
SZ	32	3 (0); 3 (1); 19 (2)	38	33 (0); 4 (1); 0 (2)
BD	36	5 (0); 5 (1); 18b (2)	47	9 (0); 20 (1); 6 (2)
HC	36	10 (0); 8 (1); 16 (2)	34	20 (0); 11a (1); 1a (2)

Abbreviations: BD, bipolar disorder; HC, healthy controls; HERV-W, Human Endogenous Retrovirus type-W; PBMC, peripheral mononuclear cell; RT–PCR, reverse transcriptase PCR; SZ, schizophrenia.

Clones were obtained in PBMC from three HC, three BD and four SZ individuals. According to software analyses (Mac Vector V.11.1.1, Cambridge, NC, USA) amplicons with a maximum of two nucleotide substitutions could hybridize with the probe used in the quantitative PCR assay. The number of clones are indicated followed by the corresponding number of substituted nucleotides between brackets for 0, 1 and 2 possible substitutions.

Detailed sequences with alignments are presented in Supplementary Information.

^aNucleotide substitutions never found in RNA from SZ, but in 19 clones from BD RNA. This sequence is nonetheless present in DNA: one clone from SZ, three clones from BD and two clones from HC.

^bClones with two nucleotide substitutions from BD DNA are all identical, but never found in clones from RNA (BD, SZ or HC ). They are present in 14/19 clones from SZ DNA and 14/16 clones from HC DNA.